• Title, Summary, Keyword: ionic cluster

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Ionic Cluster Mimic Membranes Using Ionized Cyclodextrin

  • Won Jong-Ok;Yoo Ji-Young;Kang Moon-Sung;Kang Yong-Soo
    • Macromolecular Research
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    • v.14 no.4
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    • pp.449-455
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    • 2006
  • Ionic cluster mimic, polymer electrolyte membranes were prepared using polymer composites of crosslinked poly(vinyl alcohol) (PVA) with sulfated-${\beta}$-cyclodextrins (${\beta}-CDSO_3H$) or phosphated-${\beta}$-cyclodextrins (${\beta}-CDPO(OH)_2$). When Nafion, developed for a fuel cell using low temperature, polymer electrolyte membranes, is used in a direct methanol fuel cell, it has a methanol crossover problem. The ionic inverted micellar structure formed by micro-segregation in Nafion, known as ionic cluster, is distorted in methanol aqueous solution, resulting in the significant transport of methanol through the membrane. While the ionic structure formed by the ionic sites in either ${\beta}-CDSO_3H$ or ${\beta}-CDPO(OH)_2$ in this composite membrane is maintained in methanol solution, it is expected to reduce methanol transport. Proton conductivity was found to increase in PVA membranes upon addition of ionized cyclodextrins. Methanol permeability through the PVA composite membrane containing cyclodextrins was lower than that of Nafion. It is thus concluded that the structure and fixation of ionic clusters are significant barriers to methanol crossover in direct methanol fuel cells.

A Study on Friction-induced Surface Fracture Behaviors of Carboxylic Acid Modified Styrenic Thermoplastic Elastomer as Additives (첨가제에 따른 변성 스티렌계 열가소성 엘라스토머의 마찰에 의한 표면 파괴 거동 연구)

  • Jeon, Jun-Ha;Park, Sang-Min;Lee, Jin- Hyok;Um, Gi-Yong
    • Journal of Adhesion and Interface
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    • v.16 no.3
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    • pp.95-100
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    • 2015
  • In this work, we observed the effect of silica, zinc oxide, zinc ion coated silica on carboxylic acid modified styrenic thermoplastic elastomer (m-TPS) film for friction-induced surface fracture. m-TPS film added general silica showed poor mechanical properties, anti-abrasion and friction-induced surface fracture, caused by strong filler-filler interaction of silica. In case of m-TPS films added zinc oxide or zinc ion coated silica, mechanical properties, anti-abrasion and friction-induced surface fracture were improved due to forming ionic cluster between carboxylic acid group of m-TPS and zinc ion. Ionic cluster were confirmed by FT-IR analysis that observed zinc carboxylated group stretch peak at $1550{\sim}1650cm^{-1}$.

Dynamic Mechanical and Morphological Studies of Styrene-co-Methacrylate and Sulfonated Polystyrene Ionomers Containing Aliphatic Dicarboxylate Salts

  • Luqman, Mohammad;Kim, Joon-Seop;Shin, Kwan-Woo
    • Macromolecular Research
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    • v.17 no.9
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    • pp.658-665
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    • 2009
  • This study examined the effects of the sodium salts of aliphatic dicarboxylic acids (DCAs) on the dynamic mechanical properties and morphology of two sets of poly(styrene-co-sodium methacrylate) (MNa) and poly(styrene-co-sodium styrenesulfonate) (SNa) ionomers. When the DCA content was relatively low, the ionic moduli of the MNa and SNa ionomers increased but the matrix and cluster glass transition temperature ($T_g$) did not change significantly. The increasing ionic modulus was almost independent of the type of the ionic groups of the ionomer, and the chain length of DCAs. When a large amount of the sodium succinate (DCA4) was added to the MNa and SNa ionomers, the ionic moduli of the two ionomers increased strongly but the matrix and cluster $T_g's$ increased slightly and significantly, respectively. In the case of sodium hexadecanedioate (DCA 16), DCA 16 increased the ionic moduli of the two ionomers. The addition of DCA16 changed the matrix and cluster $T_g's$ of the MNa ionomer slightly, but decreased the cluster $T_g$ of the SNa ionomer significantly with no change in the matrix $T_g$. In addition, the DCA-containing ionomers showed an X-ray diffraction peak indicating the presence of ordered domains of DC As in the ionomers. Hence, DCA4 acts mainly as a reinforcing filler in MNa and SNa systems. In the case of DCA 16, it initially behaved like a filler but also functioned as a preferential plasticizer for the clusters at high content.

Preparation and Characterization of Nafion Composite Membranes Containing 1-ethyl-3-methylimidazolium Tetracyanoborate

  • Shin, Mun-Sik;Park, Jin-Soo
    • Journal of the Korean Electrochemical Society
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    • v.15 no.1
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    • pp.35-40
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    • 2012
  • The composite membranes using Nafion as matrix and 1-ethyl-3-methylimidazolium tetracyanoborate (EMITCB) as ion-conducting medium in replacement of water were prepared and characterized. The amount of EMITCB in Nafion varied from 30 to 50wt%. The composite membranes are characterized by ion conductivity, thermogravitational analyses (TGA) and small-angle X-ray scattering (SAXS). The composite membranes containing EMITCB of 40wt% showed the maximum ionic conductivity which was ~0.0146 S $cm^{-1}$ at 423.15 K. It is inferred that the decrease in ionic conductivity of all the composite membranes might be due to the decomposition of a tetracyanoboric acid formed in the composite membranes. The results of SAXS indicated that the ionic clusters to conduct proton in the composite membranes were successfully formed. In accordance with the results of ionic conductivity as a function of a reciprocal temperature, SAXS showed a proportional decrease in scattering maximum $q_{max}$ as the amount of EMITCB increases in the composite membranes, which results in the increase in ionomer cluster size. The TGA showed no significant decomposition of the ionic liquid as well as the composite membranes in the range of operating temperature ($120-150^{\circ}C$) of high temperature proton exchange membrane fuel cells (HTPEMFC). As a result, EMITCB is able to play an important role in transferring proton in the composite membranes at elevated temperatures with no external humidification for proton exchange membrane fuel cells.

The Effect of Aggregation States on ionic Conductivity of Stolid Polymer Electrolytes Based on Waterborne Polyurethane

  • Bae, Sang-Sik;Jo, Nam-Ju
    • Macromolecular Research
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    • v.9 no.6
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    • pp.332-338
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    • 2001
  • Waterborne polyurethane as a new polymer electrolyte was synthesized by using relatively hydrophilic polyols. The morphology of polyurethane was changed as it was dispersed in water. In contrast to polyurethane ionomer, waterborne polyurethane did not form an ionic cluster but produced a binary system composed of hydrophilic and hydrophobic groups. In the colloidal system, the former and the latter existed at outward and inward, respectively. Waterborne polyurethane was prepared from poly(ethylene glycol) (PEG) /poly(propylene glycol) (PPG) copolymer, 4,4'-diphenylmethane diisocyanate(MDI), ethylene diamine as a chain extender, and three ionization agents, 1,3-propane sultone, sodium hydride and lithium hydroxide. PEG/PPG copolymer was used for suppressing the crystallinity of PEG and N-H bond was ionized for increasing the electrochemical stability of polyurethane. Low molecular weight poly(ethylene glycol) and poly(ethylene glycol dimethyl ether) (PEGDME) were used as plasticizers. DSC, FT-IR and $^1$H-NMR of the waterborne polyurethane were measured. Also, the ionic conductivity of solid polymer electrolytes based on waterborne polyurethane and various concentrations of low molecular weight poly(ethylene glycol) or PEGDME were measured by AC impedance.

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Thermo-reversible Crosslinking Elastomer through Supramolecular Networks (초분자 네트워크를 이용한 열가역성 가교 탄성체)

  • Bae, Jong-Woo;Oh, Sang-Taek;Kim, Gu-Ni;Baik, Hyen-Jong;Kim, Won-Ho;Choi, Sung-Seen
    • Elastomers and Composites
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    • v.45 no.3
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    • pp.165-169
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    • 2010
  • Recently supramolecular network thermo-reversible crosslinking elastomer having flexibility, various functionality, and advantages of thermoplastic elastomer (TPE) such as recycle and easy processbility is introduced. Although thermo-reversible bonds such as hydrogen bond and ionic cluster is recognized as a common technology since 1990, control technology of bonding and dissociation of crosslink in supramolecular network is a recent technology. In this review, characteristics of thermo-reversible crosslinking elastomer having rheological properties of TPE and reinforcing behaviors of thermoset elastomer are summarized.

Permeation Property of Ionomer Film with New Multifunctional Ionic Site (다관능기를 도입한 아이오노머 필름의 기체투과 특성)

  • Lee, Bo-Mi;Jeong, Sam-Bong;Nam, Sang-Yong
    • Korean Journal of Materials Research
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    • v.22 no.5
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    • pp.227-236
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    • 2012
  • Ionomer is a thermoplastic that is composed of covalent bonds and ionic bonds. It is possible to use this material in processes such as injection molding or extrusion molding due to the material's high oil resistance, weatherproof characteristics, and shock resistance. In this study, a new ionomer having a multifunctional group was prepared by a stepwise neutralization system with the addition of acidic and salt additives. In step I, to increase the contents of the multifunctional group and the acid degree in ethylene acrylic acid (EAA), MGA was added to the ionomer resin (EAA). A new ionomer was prepared via the traditional preparation method of the ionic cross-linking process. In step II, metal salt was added to the mixture of EAA and MGA. The extrusion process was performed using a twin extruder (L/D = 40, size : ${\varphi}30$). Ionomer film was prepared for evaluation of gas permeability by using the compression molding process. The degree of neutralized and ionic cross-linked new ionomer was confirmed by FT-IR and XRD analysis. In order to estimate the neutralization of the new ionomer film, various properties such as gas permeation and mechanical properties were measured. The physical strength and anti-scratch property of the new ionomer were improved with increase of the neutralization degree. The gas barrier property of the new ionomer was improved through the introduction of an ionic site. Also, the ionic degree of cross-linking and gas barrier property of the ionomer membrane prepared by stepwise neutralization were increased.

Infrared Multiphoton Dissociation Spectroscopy of Protonated 1,2-Diaminoethane-water Clusters: Vibrational Assignment via the MP2 Method

  • Boo, Bong Hyun;Kang, Sukmin;Furuya, Ari;Judai, Ken;Nishi, Nobuyuki
    • Bulletin of the Korean Chemical Society
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    • v.34 no.11
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    • pp.3327-3334
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    • 2013
  • Infrared multiphoton dissociation (IRMPD) spectra of various protonated 1,2-diaminoethane-water clusters DAE-$H^+-(H_2O)_n$ (n = 1-6) were measured in the wavelength range of 3000-3800 $cm^{-1}$. The IRMPD spectra of the well separated ionic clusters were simulated by the MP2 method employing various basis sets. Comparison of the IRMPD spectra with the theory indicates that each cluster may exist as several low-lying conformers, and the sum spectra of the various conformers reveal almost one to one correspondence between theory and experiment. Free N-H and O-H stretches are observed in the ranges of 3400-3500 and 3600-3800 $cm^{-1}$, respectively. The $O-H{\cdots}N$ and $N-H{\cdots}O$ stretches are, however, observed in the broad region of 3000-3600 $cm^{-1}$. The theoretical calculations on DAE-$H^+-(H_2O)_n$ (n = 1-4) show gradual decrease of the average binding energy between DAE-$H^+$ and $H_2O$ as the cluster size increases, attaining the lowest value of 55 kJ/mol when n = 4. We found a low energy barrier of 21 kJ/mol to the isomerization converting the lowest energy cluster of DAE-$H^+-(H_2O)_n$ to the second lowest one.

The Characterization of Crosslinked SPEEK Based Ion Exchange Membranes Prepared by EB Irradiation Method (전자선을 이용해 가교된 SPEEK 기본 물질로 하는 이온 교환막의 특성 분석)

  • Song, Ju-Myung;Shin, Junhwa;Sohn, Joon-Yong;Nho, Young-Chang
    • Journal of Radiation Industry
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    • v.5 no.2
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    • pp.151-157
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    • 2011
  • Crosslinked SPEEK/PVDF membrane were prepared by EB radiation method with various contents of PVDF. The prepared membranes were subjected to a comparative study of proton exchange membranes for fuel cell appreciations. The crosslinked SPEEK/PVDF membranes were characterized by using DMA, DSC and SAXS. The DMA data indicate that the ionic modulus values and cluster $T_g$ decrease with increasing PVDF content. Thus, it was suggested that the number of clustering in the crosslinked membranes can be reduced with increasing PVDF content. The DSC results were shown that the degree of crystalline of the membrane increased with increasing PVDF content. The morphology of the crosslinkied membranes was shown that with increasing PVDF content, the number of crystalline domain of the SPEEK/PVDF membranes increased but ionic aggregation of the membranes decreased. The water uptake behavior, ionic exchange capacity (IEC) and proton conductivity were decreased with increasing PVDF content. The overall findings suggest that the crosslinked membranes offer the possibility for improving the performance of PEMFC, provided that the membranes have thermal and hydration stability.